Canada's Ebola vaccine: How does it work?

A healthcare worker, right, wears protective gear against the Ebola virus before he enters the Ebola isolation ward at Kenema Government Hospital, in Kenema, the Eastern Province around 300km from the capital city of Freetown in Sierra Leone, Tuesday, Aug 12, 2014. (AP / Michael Duff)

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Human clinical trials of an experimental Canadian Ebola vaccine are underway, with officials saying that if successful the vaccine could be shipped to affected areas of West Africa within a few months.

Here are more details about the VSV-EBOV vaccine and the clinical trials:

How big will the trial be and where will it take place?

Health Minister Rona Ambrose said that 20 vials of the vaccine will be tested on 40 healthy volunteers at the Walter Reed Army Institute of Research in Maryland.

The trial, known as a Phase 1 trial, is designed to determine if VSV-EBOV is safe for human use. It is also designed to determine the right dosage for humans and to look out for any side effects.

When will the results of the trial be known?

Dr. Gregory Taylor, Canada's Chief Public Health Officer, said results from the trial could be available by December.

If those results show that the vaccine is successful, the next step would be to test it in a larger group, including people who have had direct contact with Ebola patients in West Africa.

Will there be other trials for the vaccine?

NewLink Genetics, the U.S. firm that holds the licence for the vaccine, said earlier in October that there will be at least five clinical trials for VSV-EBOV. These will take place in the U.S., Germany, Switzerland and an African country not currently affected by the outbreak.

How does the vaccine work?

Last August, Dr. Gary Kobinger, chief of special pathogens at The Public Health Agency of Canada shared details about how the vaccine works.

He said the vaccine can be administered before exposure to the Ebola virus, and in animal models it has also shown efficacy after exposure.

"It can have action on both sides, a little bit like the rabies vaccine," he said.

The vaccine does not contain any live Ebola virus, and is instead made up of dead parts of the virus, combined with another virus typically found in animals.

Kobinger said the scientists who are developing the vaccine do not yet fully understand the vaccine's precise mechanism, but there are a number of hypotheses they are studying.

One hypothesis is that the "extremely potent" vaccine stimulates an immune response to protect the individual against the virus in a sort of "race," he said.

In this model, the individual will be protected if their immune response develops fast enough and before the virus grows.

The second hypothesis being considered is based off of a model in which the vaccine "competes" with the virus for target cells, which replicate the virus.

If we don't fully understand it, is it safe?

In August, Kobinger noted that in the clinical development of any new vaccine the first step is to establish efficacy. Once that has been established, researchers typically work on establishing the vaccine's safety for human use.

The scientists behind VSV-EBOV have been researching its safety for about a year now, he said, noting that efficacy and safety are measured separately.

"Safety is completely different than efficacy," Kobinger said. "The safety and efficacy of a vaccine don't necessarily go together, so you can't judge the safety based on efficacy."

The vaccine has never before been tested in humans in the context of safety trials, however there was one individual who received the vaccine after lab exposure to the virus in Germany, he said.

That person did not go on to develop Ebola, and did not experience any known severe adverse events, Kobinger said.

He added that the vaccine has been tested in animals, and researchers have not recorded any serious adverse events from those animal trials.